The present disclosure relates to an image forming apparatus.
As an example of electro-photographic image forming apparatuses such as a copier and a printer, there has been known an intermediate-transfer type image forming apparatus which primarily transfers toner images of different colors, respectively formed by a plurality of image forming portions, onto an intermediate transfer belt to be sequentially superimposed one on another on the intermediate transfer belt, which is arranged along the plurality of image forming portions, and then secondarily transfers the toner images from the intermediate transfer belt onto a sheet. About the image forming apparatus of this type, it is feared that there is a risk of the intermediate transfer belt meandering or twisting. To cope with this risk, there have been proposed image forming apparatuses capable of suppressing occurrence of meandering and twisting of the intermediate transfer belt.
In an example of such image forming apparatuses, of an outer circumferential surface of a roller around which a belt is wound, a central part in a rotation-axis direction is a high friction-coefficient surface, and opposite side parts in the rotation-axis direction are low friction-coefficient surface. Thus, the roller exerts a stronger belt conveying force in its central part than in its opposite side parts, and as a result, the belt is constantly being drawn toward the central part of the roller. This function helps prevent meandering of the belt.